Destruction of nematodes



United States Patent 3,303,601 DESTRUCTION 0F NEMATODES Whitney H.Mears, Morris Plains, N.J., assignor to Allied Chemical Corporation, NewYork, N.Y., a corporation of New York No Drawing. Filed Sept. 21, 1965,Ser. No. 489,039 3 Claims. (Cl. 43132) This invention relates to thetreatment of aqueous media containing nematodes and, more specifically,to the destruction of nematodes in said aqueous media.

Ultrasonic vibrations have been suggested for pest control in view ofthe fact that ultrasonics do not contaminate the medium in which theyare used and do not require high, and, consequently, unsafe voltages fortheir operation. The use of ultrasonics has been limited, however, dueto the lack of a specific effective mode of application and has not beenused heretofore for the destruction of nematodes.

An object of this invention is to provide a method for the destructionof nematodes by ultrasonic vibration. A further object of this inventionis to provide a method for the destruction of nematodes in an aqueousmedium. Other objects and advantages will become apparent hereinafter.

In accordance with the invention, a method for the destruction ofnematodes has been found which comprises applying modulated ultrasonicwaves, at a frequency of about to about 100 kilocycles per second and ata power of about 50 to about 200 watts per gallon of aqueous medium, tosuch aqueous medium containing nematodes, for about 0.25 to about 10minutes.

A more detailed description of the invention follows:

Water, or other aqueous media, containing the nematodes in anyproportion can be run into a tank or pipe of known capacity. Anultrasonic generator is then attached to a transducer or a plurality oftransducers which are inserted into the tank or pipe. The number oftransducers can be determined by: (a) the capacity of the tank orsection of the pipe, conveniently measured in gallons, to which theultrasonic treatment is to be applied; (b) the power transmitted throughthe transducer; and (c) the rate of flow of the aqueous medium if suchmedium is not stationary. A transducer transmitting about 50 to about200 watts per gallon of aqueous medium is effective providing theaqueous medium is in the transducer field for about 0.25 to about 10minutes.

The number of watts per gallon of water transmitted by a transducer isdetermined as follows:

Energy appiled rated power output efficiency volume time tank volumeUnits can be watts, gallons, and minutes. Efficiencies of the generatorsare about 85%. It is assumed in this formula that energy is uniformlydistributed over the tank volume. The energy applied must be taken as anestimate since sound can have maximum and minimum pressure regionsdepending on the wave lengths which can travel across the tank. FMmodulation gives a wider band of frequencies than does AM modulationwith consequent increased uniform distribution of power.

It is not understood why the foregoing combination of variables iseffective. It can only be theorized that unmodulated waves give poorvolume coverage; optimum carrier frequencies are dependent on therelationship of the corresponding wave lengths to the dimensions of thecontainer; and the reflection of sound Waves complicates the intensitypattern.

It is advantageous to get an even distribution of the ultrasonic wavesin the field which is bounded by the dimensions of the tank or by thepipe section, i.e., the full effect of the ultrasonic waves ispreferably concentrated on the entire field as designated. Thetransducer can be conveniently placed in the corner of thethree-dimensional area, which it is to service. This permits the powerto be evenly distributed throughout the area. The transducer radiationpatterns are not uniform but look like flashlight patterns with a wideangle of spread. Usually the waves radiate out into one half of a sphereand back-radiation is minimal. In the case of unidirectionaltransducers, the unit can be located in the lower corner of arectangular tank and in the case of a transducer with a circularpattern, the transducer can be located in the center of a tank at amiddle depth. The three-dimensional area is preferably as close to cubicor spherical in shape as practicable so that the distance from thetransducer to the boundaries of the area are approximately equidistant.Where larger volumes are contemplated, each transducer can be placed inthe center of the area, which the ultrasonic vibrations of theparticular transducer are to influence. A matrix-like arrangement oftransducers can be availed of in this event. Economy and simplicitysuggest that a small tank which is constantly emptied and refilled or anarrow cross section of pipe give the most practicable application sincea smaller number of transducers can service these areas and the capacityof the generator to power these transducers does not have to be sogreat. Where the aqueous medium is flowing through a pipe of narrowcross section, the transducers can be arranged along the path of thepipe so that the aqueous medium is continuously in the ultrasonic wavefield for the required period of time.

It has been found that one transducer transmitting about 50 to about 200watts per gallon of aqueous medium is satisfactory to accomplish theobjective in a tank where the liquid medium is stationary although suchtank can be emptied and refilled with different batches of water afterthe ultrasonic treatment is accomplished. Where the water is flowingthrough a pipe the number of transducers necessary is determinedaccording to the power of the transducer, the area of the cross sectionof the pipe, and the rate of flow of the aqueous medium through thepipe, i.e., each gallon of aqueous medium must be in the ultrasonicfield for about 0.25 to about 10 minutes.

The range of frequencies which can be used must be from about 10 toabout 100 kilocycles per second. The preferred range is from about 20 toabout kilocycles per second. The ultrasonic waves must be modulated,i.e., either amplitude modulated or frequency modu lated, with thelatter modulation being preferred. The modulation is accomplished by theintroduction of a wave whose frequency swings from about a carrierfrequency of +50% down to about a carrier frequency of 50% at a swingrate of 10 to 10,000 cycles per second and is preferably 60 cycles persecond. The preferred frequency modulation ranges from about 40+15kilocycles per second to about 40-15 kilocycles per second and ispreferably about 40: 15 kilocycles per second at 60 cycles second, Asnoted, the time required for exposure to the modulated ultrasonic fieldis from about 0.25 to about 10 minutes. The preferred time for exposureto the amplitude modulation modulated ultrasonic field is from about0.50 to about 5 minutes. The preferred time for exposure to thefrequency modulated ultrasonic field is from about 0.25 to about 2minutes.

Example I Table I describes four units each of which includes anultrasonic generator, a transducer, and a tank. The

3 ultrasonic generators used in this example were manufactured by theNarda Ultrasonic Corp. of Westbury, New York.

4 medium are generally opaque under low power magnification, beingfilled with food base. Treated nematode suspensoids were examined undera binocular micro- TABLE I Generator Characteristics TransducerCharacteristics I Tank Unit Frequency, Modulation Watts Efficiency,Number of Watts (Gallon KC./Sec. Percent Transducers per Gal. Capacity)1 20 AM 60 c.p.s 500 85 8 110 4 2 40 AM 60 c.p.s 500 85 8 110 4 8 90wave AM 60 c.p.s 50 85 1 170 M 4 40:1;15 FM 60 c.p.s 300 85 8 60 4 TableII shows the destruction of nematodes by ultra- 15 scope to determinethe percent kill by the ultrasonic sonic radiation using the uni-tsdescribed in Table I.

TABLE II Unit Time Cycle Percent Kill 1. 1 min. 60 1 5 min 2. 1 min- 902 2 min 95 min. 100 15 sec. on; 10 sec. on; see. on 1 min 98 l min., 25sec 99 2 min. (l'ocussed) 90 2 min. +1 min. (interrupted)- 98 5 min- 1001 min 100 4. 1 min 100 4 30 sec 100 4 10 sec- 79 1 Not efiective. Norm:

Kc./sec.=kilocycles per second. AM=amplitude modulation. FM=trequencymodulation. C.p.s.=cycles per second. Gal.=gallon.

Min.=minutes.

Sec.=seconds.

Focussed is defined as a narrow transducer beam angle of about degrees.The tank is therefore not covered by radiation but the radiation in someareas is more intense.

The tests shown in Table 11 above were accomplished with the use of apure culture of the sour paste nematode, Panagrellus redivivus. Thisculture was grown on an oatmeal medium and the resultant nematodes wereused as test organisms. The nematodes were separated from the oatmeal bywashing and settling in a water column. After separation, the nematodeswere diluted in distilled water to a concentration of approximately perml. and were used in this solution in the tests set forth above in TableII. Nematodes grown on an oatmeal treatment. Dead nematodes weredetermined by observing their activity, i.e., these nematodes when alivegenerally oscillate at the rate of 120 times per minute; by theirappearance, which is translucent with the body wall ruptured and theinternal body contents removed; and by their failure to revive one hoursubsequent to treatment.

I claim:

1. A method for the treatment of an aqueous medium containing nematodescomprising applying modulated ultrasonic waves, at a frequency of about10 to about kilocycles per second and at a power of about 50 to about200 watts per gallon of aqueous medium, to the aqueous medium containingnematodes for about 0.25 to about 10 minutes, whereby the nematodes aredestroyed,

2. A method for the treatment of an aqueous medium containing nematodesas defined in claim 1 wherein the modulated ultrasonic waves areamplitude modulated.

3. Amethod for the treatment of an aqueous medium containing nematodesas defined in claim 1 wherein the modulated ultrasonic waves arefrequency modulated.

References Cited by the Examiner UNITED STATES PATENTS 2,424,375 7/1947Van Allen 116-437 2,448,372 8/ 1948 Horsley 99-217 X 2,585,103 2/1952Fitzgerald 99217 X 2,715,384 8/1955 Meng 99217 X 2,922,999 1/1960 Carlin340-384 FOREIGN PATENTS 474,187 10/ 1937 Great Britain.

SAMUEL KOREN, Primary Examiner.

F. MEDEERY, Examiner,

1. A METHOD FOR THE TREATMENT OF AN AQUEOUS MEDIUM CONTAINING NEMATODESCOMPRISING APPLYING MODULATED ULTRASONIC WAVES, AT A FREQUENCY OF ABOUT10 TO ABOUT 100 KILOCYCLES PER SECOND AND AT A POWER OF ABOUT 50 TOABOUT 200 WATTS PER GALLON OF AQUEOUS MEDIUM, TO THE AQUEOUS MEDIUMCONTAINING NEMATODES FOR ABOUT 0.25 TO ABOUT 10 MINUTES, WHEREBY THENEMATODES ARE DESTROYED.